The present invention relates to improvements in rolling gates or doors which serve as security closures for store fronts, building entrances and the like.
Rolling gates or doors are normally made in open grille form, and consist of an articulated metal grid structure composed of spaced horizontal and vertical metal rods interconnected by links to enable the grille to be rolled up to an open position and rolled down to a closed position. When employed as a security gate for a store front, the grille covers over both the door and store front window in order to prevent unauthorized access to the store through the door or window. Conventionally, such gates comprise an open metal grid or grille structure which enables the public to view the window displays of the store through the grille even though the store is closed and the security gate is locked in lowered position.
Examples of conventional open-work articulated rolling grilles of the aforementioned type are shown, for example in U.S. Pat. Nos. 2,898,988, 3,601,175 and 3,850,465. Because of their reticulated construction, such grilles have the advantage of providing a clear view of the store front covered by the grille, as well as the ready passage of light through the grille. However, they have the disadvantage of impaired security. Prowlers are able to insert a bar or other object through the open spaces between the bars and links in order to break through the store window and can then insert a long hook or other tool through the grille opening and the broken window for the purpose of removing merchandise from the window display.
Attempts have been made to solve this problem by providing rolling gates with articulated horizontal slats or panels made of metal and each having a row of spaced rectangular apertures constituting windows through which persons in the street can see the store front covered by the gate. In some instances, these window apertures are filled with panes of glass or transparent plastic which add a security feature in preventing persons outside the closed gate from reaching through the rectangular apertures. Rolling gates of this type are shown in U.S. Pat. Nos. 1,352,656 issued Sept. 14, 1920 and 2,592,888 issued Apr. 15, 1952. Gates with such panel window apertures do not, however, provide adequate visibility, and further are expensive in manufacture.
In U.S. Pat. No. 4,120,340, there is disclosed a rolling grille composed of a series of horizontal metal rods interconnected at several intermediate points by a plurality of metal links to form the grillework structure. A transparent panel is disposed between each pair of adjacent rods and is connected at its ends between each pair of adjacent links so that the grille is formed of a large number of small transparent panels aligned in columns and rows. While the transparent panels of this rolling grille prevent penetration of the grille for security purposes, and at the same time provide acceptable visibility through the grille, the inherent structural requirements of the grille result in high manufacturing costs. To enable the grille to be rolled up in stored condition, the horizontal rods are in practice spaced approximately three to nine inches apart, and to provide a grille of suitable strength, the vertical chains of links are spaced apart by distances between one and one-half inches to twelve inches. Consequently, for a conventional grille of fifteen foot height, hundreds of transparent panels are required, each panel being individually connected between a pair of adjacent links. Assembly of these grilles within a store front is also difficult and time-consuming.